The transmission of two dimensional images over communication media necessitates the translation of the image into a signal format such that it can be most effectively restored to its two dimensional form at the receiver. Two dimensional images are commonly scanned and converted from an analog representation to a digital representation of the image on a point by point basis. The elements of such a digital signal, representative of each elemental point of the image, usually identify a binary black or white level. Such a digital representation contains large amounts of redundant information. A typical image may require some 500,000 or more electrical points to attain the necessary resolution.
One technique disclosed in the prior art for reducing the redundancy of a point to point image representation is to scan the image in contiguous small areas of successive blocks of elements and to encode those blocks which match one of a selected vocabulary of simple geometric patterns. A problem which arises with such prior art technique is that in order to represent each possible geometric pattern which may occur in a data block, a prohibitively large library of reference geometric patterns must be stored.